UC Davis Institute of Transportation Studies

Zero and near-zero emission vehicles based on electric-drive technology have the potential to play a long-term role in alleviating the air pollution, greenhouse gas, and energy use concerns associated with conventional vehicles. Most attention has focused on electric-drive technologies for light-duty vehicles (LDVs), but some electric-drive technologies are also suitable for heavy-duty vehicle (HDV) applications.

HDVs are in fact particularly attractive targets for zero-emission technology because they produce a disproportionate share of motor vehicle pollution in California and the U.S. HDVs are largely based on diesel engine technology, and these diesel engines produce high emission levels of oxides of nitrogen (NOx) and fine particulates (PM10). PM10 emissions in particular are increasingly seen as having the most serious health effects of all vehicle pollutants. Furthermore, the vast majority of HDV travel is by heavy-duty trucks (HDTs), but these vehicles are at present less-stringently regulated than urban transit buses (particularly given the recent CARB regulation to reduce urban transit bus emissions beginning in 2002).

In order to investigate the potential of stimulating the development of zero-emission HDTs, and their introduction into California-based HDT fleets, this report anlayzes the potential for broadening the ZEV mandate to allow manufacturers of zero-emission HDTs to be awarded ZEV credits. The report analyzes the average relative emission levels of carbon monoxide (CO), hydrocarbons (HCs), NOx, and PM10 from LDVs and HDTs in California, as estimated in the latest version of the CARB mobile source emission inventory model, EMFAC2000. Using these estimates of the relative emission reduction potential of zero-emission LDVs and medium and heavy HDTs, along with estimates of the average annual mileage for these vehicle classes, potential ZEV credit award levels for zero-emission HDTs are estimated.

The findings are that from 42 to 226 ZEV credits could in principle be justified to be awarded to manufacturers of zero-emission HDTs, depending on the model year of their introduction (from 2001 to 2010) and the HDT weight class, if the four pollutants are weighted according to their approximate relative damage values. These damage values reflect the impact on each pollutant to human health in major California urban areas. Using a simpler scheme that does not consider the relative damages from the pollutants, and that weights each pollutant equally, potential ZEV credit award levels range from 24 to 100 credits for zero-emission HDTs.